JP6537331B2 - Optical system and imaging apparatus having the same - Google Patents

Description

  The present invention relates to an optical system, and is suitable, for example, for an imaging optical system used in an imaging device such as a silver halide film camera, a digital still camera, a digital video camera, a surveillance camera, and a TV camera.

  In recent years, an optical system used for an image pickup apparatus is required to have a wide angle of view that allows the entire system to be compact and easy to capture a wide range. For example, video cameras and in-vehicle cameras are required to have a wide angle of view of 120 ° or more for capturing a wide area, and small distortion to improve visibility around the screen. ing. Heretofore, as an optical system satisfying these requirements, an optical system comprising a front group having negative refractive power, an aperture stop, and a rear group having positive refractive power in order from the object side to the image side is known (Patent Document 1) , 2).

  In Patent Document 1, a negative lens, a cemented lens of a positive lens and a negative lens, an aperture stop, a positive lens, and a cemented lens of a positive lens and a negative lens are arranged in order from the object side to the image plane side. A wide angle lens of ~ 180 ° is disclosed. Patent Document 2 discloses a super-wide-angle lens composed of a negative lens, a negative lens, a positive lens, a positive lens, and a cemented lens of a negative lens and a positive lens in order from the object side to the image plane side and having a shooting angle of view of 140 °. It is done.

Unexamined-Japanese-Patent No. 2004-145256 JP-A-4-267212

  In the wide angle optical system, a front group having negative refractive power is disposed on the object side with respect to the aperture stop, and a rear group having positive refractive power is disposed on the image side. Since the arrangement of refractive powers is asymmetric across the aperture stop, the occurrence of various aberrations due to asymmetry such as coma, distortion and lateral chromatic aberration tends to increase. In particular, when trying to shorten the total lens length while achieving a wide angle of view, the refractive power of the negative lens on the object side becomes strong, the refractive power of the positive lens on the image side becomes strong, and it is difficult to keep distortion small become.

  In Patent Document 1, a cemented lens of positive refractive power is disposed closest to the image. Then, assuming that the image height is Y, the focal length of the entire system is f, and the half angle of view is ω, distortion aberration is −48% to −48 in central projection with Y = f × tan (ω) as the ideal image height. It is set at 85% to reduce distortion while maintaining a wide angle of view.

  Further, in Patent Document 2, a cemented lens of positive refractive power is disposed closest to the image. The distortion is set to -70% by the central projection method in which Y = f × tan (ω) is the ideal image height, and the distortion is reduced while the wide angle of view is obtained. However, in the patent documents 1 and 2, when trying to shorten the total lens length while maintaining a wide angle of view, the refractive power of the negative lens close to the object side and the refractive power of the positive lens close to the image surface side become strong. Aberrations increase.

  In order to reduce distortion aberration over the entire screen and achieve high optical performance while reducing the overall length of the lens while reducing the overall size of the system, the lens groups in front of and behind the aperture stop in the optical system are used. It is important to set the lens configuration properly. If these settings are not appropriate, it becomes difficult to obtain an optical system having a small size, wide angle of view, low distortion, and high optical performance.

  An object of the present invention is to provide an optical system which is small in size and has a wide angle of view and which is easy to obtain a high quality image over the entire screen with little distortion.

The optical system of the present invention comprises a front group having negative refractive power, an aperture stop, and a rear group having positive refractive power, which are disposed in order from the object side to the image side, and the front group is from the object side to the image side It consists of the 1st lens, the 2nd lens, and the 3rd lens arranged in order,
The rear group comprises, in order from the object side to the image side, a fourth lens of positive refractive power and a cemented lens of negative refractive power ,
The first lens is a negative power lens with a concave surface facing the image side,
The cemented lens is formed by cementing a fifth lens of positive refractive power and a sixth lens of negative refractive power.
When the focal length of the cemented lens is f56 and the focal length of the whole system is f,
-130.0 <f56 / f <-10.0
It is characterized by satisfying the following conditional expression.

  An object of the present invention is to provide an optical system which is small in size and has a wide angle of view and which is easy to obtain a high quality image over the entire screen with little distortion.

Lens cross-sectional view when focusing on an infinite distance object in the wide-angle single-focus lens of Embodiment 1 of the present invention Aberration diagrams when focusing on an infinite distance object in the wide-angle single-focus lens of Example 1 of the present invention Lens cross-sectional view when focusing on an infinite distance object in the wide-angle single-focus lens of Embodiment 2 of the present invention The aberration figure when focusing on an infinite distance object in the wide-angle single focus lens of Example 2 of the present invention Lens cross-sectional view when focusing on an infinite distance object in the wide-angle single-focus lens of Example 3 of the present invention Aberration diagrams when focusing on an infinite distance object in the wide-angle single-focus lens of Example 3 of the present invention Lens cross-sectional view when focusing on an infinite distance object in the wide-angle single-focus lens of Embodiment 4 of the present invention Aberration diagrams when focusing on an infinite distance object in the wide-angle single-focus lens of Example 4 of the present invention Principal part schematic view of the imaging device of the present invention

Hereinafter, the best mode of the optical system of the present invention and the imaging apparatus having the same will be described. The optical system of the present invention has a front group of negative refractive power, an aperture stop, and a rear group of positive refractive power, which are disposed in order from the object side to the image side. The front group, disposed in order from the object side to the image side, a first lens having a negative refractive power with a concave surface facing the image side, the second lens, is comprised a third lens or al. The rear group includes, in order from the object side to the image side, the positive refractive power of the fourth lens, a positive cemented lens having a negative refractive power bonding the sixth lens of the fifth lens and the negative refractive power of the refractive power It consists's or et al.

  FIG. 1 is a lens sectional view of Embodiment 1 of the present invention. FIG. 2 is a longitudinal aberration diagram when focusing at infinity in Example 1; FIG. 3 is a lens sectional view of Embodiment 2 of the present invention. FIG. 4 is a longitudinal aberration diagram when focusing at infinity of Example 2; FIG. 5 is a lens sectional view of Embodiment 3 of the present invention. FIG. 6 is a longitudinal aberration diagram when focusing at infinity in Example 3; FIG. 7 is a lens sectional view of Embodiment 4 of the present invention. FIG. 8 is a longitudinal aberration diagram when focusing at infinity of Example 4; FIG. 9 is a schematic view of a camera (image pickup apparatus) provided with the optical system of the present invention.

  The optical system of each embodiment is suitable as an imaging optical system used for an imaging apparatus (optical apparatus) such as a digital still camera, a digital video camera, and a silver halide film camera. In the lens sectional view, the left side is the object side (front), and the right side is the image side (rear). The optical system of each embodiment may be used as a projection lens of a projector or the like. At this time, the left side is the screen side, and the right side is the projected image side.

  In the lens sectional view, LA is an optical system. The optical system LA is configured to have a front group FG of negative refractive power on the object side across the aperture stop SP and a rear group RG of positive refractive power on the image side. Li is the i-th lens, L23 is a cemented lens, and L56 is a cemented lens of negative refractive power. IP is an image plane, and when used as a photographing optical system of a digital video camera or digital still camera, an imaging surface of a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor The time corresponds to the film surface.

  Each longitudinal aberration diagram represents, in order from the left, spherical aberration, astigmatism, distortion, and lateral chromatic aberration. In the diagram showing spherical aberration, the solid line d represents the d-line (587.6 nm), and the two-dot chain line g represents the g-line (435.8 nm). In the diagrams showing astigmatism, solid line ΔS represents sagittal direction ΔS of d-line, and broken line ΔM represents meridional direction ΔM of d-line. Also, a diagram showing distortion represents distortion at d-line. Lateral chromatic aberration is shown for g-line with respect to d-line. Fno denotes an F number, and ω denotes a half angle of view (degree) of the shooting angle of view.

  The distortion aberration diagram shows an amount of deviation from the ideal image height as Y = f × tan (ω). In the optical system LA of each embodiment, all lenses constituting the rear group RG of positive refractive power play the same role in terms of aberration. The fourth lens L4 having a positive refractive power has an aspheric shape so that spherical aberration and coma are corrected well. The fifth lens L5 with positive refractive power uses a low dispersion material to reduce magnification chromatic aberration, and is disposed near the positive lens L4 and has a convex surface directed to the object side to reduce spherical aberration.

  The sixth lens L6 with negative refractive power corrects the chromatic aberration of magnification by using a high dispersion material, and reduces distortion by arranging the lens L6 at the most image side. The cemented lens L56 of negative refractive power corrects curvature of field by arranging a negative lens in the rear group RG of positive refractive power, and reduces distortion by arranging the lens closest to the image.

Next, lens configurations other than the above-described features of the optical system LA of each embodiment will be described.
Example 1
The first embodiment of the present invention will be described below with reference to FIGS. 1 and 2. The lens configuration is as follows from the object side to the image side. It comprises a first lens L1 of negative refractive power, a second lens L2 of negative refractive power, and a third lens L3 of positive refractive power. The rear group RG is composed of a cemented lens L56 of negative refractive power formed by cementing a fourth lens L4 of positive refractive power, a fifth lens L5 of positive refractive power and a sixth lens L6 of negative refractive power.

  The first lens L1 and the second lens L2 have a meniscus shape whose concave surface is directed to the image plane side, thereby widening a photographing angle of view and reducing distortion. The third lens L3 corrects the chromatic aberration of magnification generated by the first lens L1 and the second lens L2 by using a high dispersion material, and reduces the spherical aberration by arranging in the vicinity of the aperture stop.

Example 2
Second Embodiment A second embodiment of the present invention will be described below with reference to FIGS. 3 and 4. The lens configuration is as follows from the object side to the image side. The front group FG includes a first lens L1 of negative refractive power, a second lens L2 of negative refractive power, and a third lens L3 of positive refractive power. The rear group RG is composed of a negative refractive power cemented lens L56 obtained by cementing a fourth lens L4 of positive refractive power, a fifth lens L5 of positive refractive power and a sixth lens L6 of negative refractive power. .

  The first lens L1 and the second lens L2 have a meniscus shape whose concave surface is directed to the image plane side, thereby widening a photographing angle of view and reducing distortion. The third lens L3 corrects the chromatic aberration of magnification generated by the first lens L1 and the second lens L2 by using a high dispersion material, and reduces the spherical aberration by arranging in the vicinity of the aperture stop SP.

[Example 3]
The third embodiment of the present invention will be described below with reference to FIGS. 5 and 6. The lens configuration is as follows from the object side to the image side. The front group FG is composed of a cemented lens L23 in which a first lens L1 of negative refractive power, a second lens L2 of positive refractive power, and a third lens L3 of negative refractive power are cemented. The rear group RG is composed of a negative refractive power cemented lens L56 obtained by cementing a fourth lens L4 of positive refractive power, a fifth lens L5 of positive refractive power and a sixth lens L6 of negative refractive power. .

  The first lens L1 and the third lens L3 have a meniscus shape whose concave surface is directed to the image plane side, thereby widening a photographing angle of view and reducing distortion. The second lens L2 corrects the chromatic aberration of magnification generated from the first lens L1 and the third lens L3 by using a high dispersion material.

Example 4
Fourth Embodiment A fourth embodiment of the present invention will be described below with reference to FIGS. 7 and 8. The lens configuration is as follows from the object side to the image side. The front group FG includes a first lens L1 of negative refractive power, a second lens L2 of negative refractive power, and a third lens L3 of positive refractive power. The rear group RG is composed of a cemented lens L56 of negative refractive power formed by cementing a fourth lens L4 of positive refractive power, a fifth lens L5 of positive refractive power and a sixth lens L6 of negative refractive power.

  The first lens L1 and the second lens L2 have a meniscus shape whose concave surface is directed to the image plane side, thereby widening a photographing angle of view and reducing distortion. The third lens L3 corrects the chromatic aberration of magnification generated by the first lens L1 and the second lens L2 by using a high dispersion material, and reduces the spherical aberration by arranging in the vicinity of the aperture stop.

The optical system LA of each embodiment has a front group FG of negative refractive power, an aperture stop SP, and a rear group RG of positive refractive power, which are disposed in order from the object side to the image side. The front group FG is composed of a first lens L1 of negative refractive power, a second lens L2 and a third lens L3 with a concave surface facing the image plane side. The rear group RG is composed of a negative cemented lens L56 obtained by cementing a fourth lens L4 of positive refractive power, a fifth lens L5 of positive refractive power and a sixth lens L6 of negative refractive power. In the front group FA, one of the second lens L2 and the third lens L3 is a negative lens, and the other is a positive lens to reduce distortion and correct lateral chromatic aberration well. ing.

In addition, in the cemented lens L56, the curvature of field is corrected by arranging the negative lens in the rear group RG of positive refractive power, and the distortion is reduced by arranging the negative lens in the most image side. Furthermore, since the angle of incidence of the off-axis light beam on the image plane is oblique, this reduces the overall lens length. The focal length of the cemented lens L56 is f56, and the focal length of the entire system is f. At this time,
−130.0 <f56 / f <−10.0 (1)
Satisfy the following conditional expression.

  Next, the technical meaning of the above-mentioned conditional expression is demonstrated. Conditional expression (1) appropriately defines the ratio of the focal length of the entire system to the focal length of the cemented lens L56 in order to reduce distortion and shorten the overall lens length.

  If the negative refractive power of the cemented lens L56 becomes strong (if the absolute value of the negative refractive power becomes large) beyond the upper limit value of the conditional expression (1), the incident angle of the off-axis light flux on the image plane becomes large. As a result, it becomes difficult to use for an imaging device having a solid-state imaging device that requires telecentric imaging at the image plane. If the negative refractive power of the cemented lens L56 becomes weak (if the absolute value of the negative refractive power decreases) beyond the lower limit value of the conditional expression (1), it becomes difficult to reduce distortion. In addition, the incident angle of the off-axis light beam on the image plane does not become oblique incidence, and it becomes difficult to shorten the overall lens length.

More preferably, it is desirable to set the numerical range of the conditional expression (1) as follows.
−110.0 <f56 / f <−15.0 (1a)

  In the present invention, more preferably, it is desirable to satisfy one or more of the following conditional expressions. The focal length of the fifth lens L5 is f5, and the focal length of the sixth lens L6 is f6. The focal length of the fourth lens L4 is f4. Let D be the total lens length. The refractive index of the material of the sixth lens L6 is Nd6. The distance in air conversion from the lens surface on the image side of the sixth lens L6 to the image plane is taken as Sk. The front group FG has a lens Lp of positive refractive power and a lens Ln of negative refractive power disposed adjacent to the object side of the lens Lp, and the radius of curvature of the lens surface on the image side of the lens Ln is Rn, The curvature radius of the lens surface on the object side of the lens Lp is taken as Rp.

Here, in the first, second, and fourth embodiments, the lens Lp corresponds to the third lens L3, and the lens Ln corresponds to the second lens L2. In Example 3, the lens Lp corresponds to the second lens L2, and the lens Ln corresponds to the first lens L1. At this time, it is preferable to satisfy one or more of the following conditional expressions.
−1.0 <f6 / f5 <−0.7 (2)
1.2 <f4 / f <2.0 (3)
4.5 <D / f <8.0 (4)
1.85 <Nd6 <2.40 (5)
Sk / f <2.0 (6)
-10.0 <(Rn + Rp) / (Rn-Rp) <-0.8 (7)

  Next, technical meanings of the above-mentioned conditional expressions will be described. Conditional expression (2) properly defines the ratio of the focal length of the fifth lens L5 to the focal length of the sixth lens L6 in order to keep the chromatic aberration and the distortion small. When the negative refractive power of the sixth lens L6 becomes strong beyond the upper limit value of the conditional expression (2), the correction of the chromatic aberration of magnification becomes easy, but it becomes difficult to reduce the curvature of field of the color. When the negative refractive power of the sixth lens L6 becomes weak beyond the lower limit value of the conditional expression (2), it becomes difficult to reduce the magnification chromatic aberration and the distortion.

  Conditional expression (3) appropriately defines the focal length of the fourth lens L4 with respect to the focal length of the entire system in order to reduce spherical aberration. When the positive refractive power of the fourth lens L4 becomes weak beyond the upper limit value of the conditional expression (3), it becomes difficult to strengthen the negative refractive power of the cemented lens L56, and it becomes difficult to reduce distortion. Become. If the positive refractive power of the fourth lens L4 becomes strong beyond the lower limit value of the conditional expression (3), it becomes difficult to reduce the spherical aberration.

  Conditional expression (4) is for shortening the overall lens length and reducing the front lens effective diameter. If the total lens length is longer than the upper limit value of the conditional expression (4), the refractive powers of the individual lenses become weak, and it becomes difficult to miniaturize the front lens effective diameter. When the total lens length becomes short beyond the lower limit value of the conditional expression (4), the positive refractive power of the fourth lens L4 becomes strong, and it becomes difficult to reduce the spherical aberration.

  Conditional expression (5) appropriately defines the refractive index of the material of the sixth lens in order to keep the chromatic aberration small. When the refractive index of the material of the sixth lens L6 becomes high beyond the upper limit value of the conditional expression (5), the refractive power of the cemented lens surface becomes strong, and it becomes difficult to reduce the curvature of field of color. If the refractive index of the material of the sixth lens L6 decreases beyond the lower limit value of the conditional expression (5), it is difficult to reduce the radius of curvature of the cemented lens surface, and the negative refractive power of the sixth lens L6 is It becomes weak and correction of magnification chromatic aberration becomes difficult.

  Conditional expression (6) appropriately defines the distance between the sixth lens L6 and the image plane in order to shorten the total lens length. If the distance between the sixth lens L6 and the image plane becomes long beyond the upper limit value of the conditional expression (6), it is difficult to shorten the total length of the lens because the off-axis light flux does not become oblique incident on the image plane become.

  Conditional expression (7) appropriately defines the shape factor of the air lens formed between the lens Lp and the lens Ln in order to correct the field curvature well with the lens Lp. If the lens surface on the object side of the lens Lp has a strong convex shape on the object side beyond the lower limit value of the conditional expression (7), it becomes difficult to reduce distortion. If the curvature radius of the lens surface on the object side of the lens Lp becomes large beyond the upper limit value of the conditional expression (7), it becomes difficult to correct the curvature of field.

In each embodiment, it is more preferable to set the numerical ranges of the conditional expressions (2) to (7) as follows.
−0.96 <f6 / f5 <−0.75 (2a)
1.28 <f4 / f <1.92 (3a)
5.0 <D / f <7.0 (4a)
1.87 <Nd6 <2.20 (5a)
Sk / f <1.8 (6a)
−7.5 <(Rn + Rp) / (Rn−Rp) <− 0.9 (7a)

  As mentioned above, although the preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

  Next, a single-lens reflex camera as the imaging apparatus of FIG. 9 will be described. In FIG. 9, reference numeral 10 denotes an imaging optical system including the optical system 1 according to the first to fourth embodiments. The imaging optical system 10 is held by a lens barrel 2 which is a holding member. 20 is a camera body. The camera body 20 is composed of a quick return mirror 3, a focusing screen 4, a penta-dach prism 5, an eyepiece lens 6, and the like. The quick return mirror 3 reflects the light flux from the imaging optical system 10 upward. The focusing screen 4 is disposed at an image forming position of the imaging optical system 10. The penta-dach prism 5 converts the reverse image formed on the focusing plate 4 into an erect image.

  The observer observes the erected image through the eyepiece 6. The reference numeral 7 denotes a photosensitive surface, on which a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor that receives an image, or a silver halide film is disposed. At the time of photographing, the quick return mirror 3 retracts from the light path, and an image is formed by the imaging optical system 10 on the photosensitive surface 7.

  By thus applying the optical system as an imaging optical system such as a single-lens reflex camera interchangeable lens, an imaging device having high optical performance is realized. The optical system of the present invention can be applied not only to digital cameras, video cameras, cameras for silver halide films, etc., but also to optical devices such as telescopes, binoculars, copiers, and projectors. It can also be applied to mirrorless single-lens reflex cameras without quick return mirrors.

  Numerical data 1 to 4 corresponding to each of the first to fourth embodiments are shown below. In each numerical data, i represents the order of the surface from the object side, ri is the radius of curvature of the i-th (i-th surface), di is the distance between the i-th surface and the (i + 1) -th surface, ndi and didi are The refractive index and the Abbe number are shown based on the d-line. BF is a back focus in air conversion. The total lens length is a value obtained by adding a back focus value to the distance from the first lens surface to the final lens surface.

  In addition, the aspheric surface is indicated by adding a sign of * after the surface number. For the aspheric shape, X is the displacement from the surface vertex in the optical axis direction, h is the height from the optical axis in the direction perpendicular to the optical axis, r is the paraxial radius of curvature, K is the conical constant, A4, A6, When A8 and A10 are aspheric coefficients of each order,

Represented by Note that “e ± XX” in each aspheric coefficient means “× 10 ± XX”. Further, Table 1 shows numerical values corresponding to the respective conditional expressions described above.

(Numerical data 1)
Unit mm

Surface data surface number rd nd d d
1 8.880 0.60 1.77250 49.6
2 3.498 1.49
3 11.931 0.45 1.69350 53.2
4 * 2.392 1.30
5 20.368 1.06 1.88300 40.8
6-9.883 1.00
7 (F-stop) 1. 1.65
8 * 11.06 1.92 1.59201 67.0
9 *-3.260 0.10
10 8.907 2.10 1.48749 70.2
11-4.778 0.41 1.95906 17.5
12-28.415 2.45
13 0.20 1.51633 64.1
14 ∞ 1.07
Image plane ∞

Aspheric surface data surface 4
K = 0.00000e + 000A 4 =-6.00733e-004 A 6 = 4.04176e-004 A 8 =-1.37712e-004

Eighth side
K = 0.00000e + 000 A 4 = -3.41536e-003 A 6 = 9.91319e-005

9th surface
K = 0.00000e + 000 A 4 = 2.90439e-003 A 6 = -3.07623e-005 A 8 = 2.69479e-005

Various data focal length 2.43
F number 2.88
Half angle of view (degrees) 52.50
Image height 3.17
Lens total length 15.73
BF 3.65

(Numerical data 2)
Unit mm

Surface data surface number rd nd d d
1 6.642 0.60 1.77250 49.6
2 3.333 1.66
3 10.527 0.45 1.67790 50.7
4 2.451 1.34
5 121.448 0.96 1.88300 40.8
6-8.849 1.00
7 (F-stop) ∞ 1.80
8 * 10.187 2.11 1.59201 67.0
9 *-3.357 0.09
10 8.738 2.20 1.48749 70.2
11-4.250 0.46 1.89286 20.4
12 -60.727 2.65
13 0.20 1.51633 64.1
14 ∞ 1.03
Image plane ∞

Aspheric surface data surface 8
K = 0.00000e + 000 A 4 = -2.54592e-003 A 6 = 1.09793e-004

9th surface
K = 0.00000e + 000 A 4 = 2.97969e-003 A 6 =-4.04537e-005 A 8 = 2.97203e-005

Various data focal length 2.68
F number 2.88
Half angle of view (degree) 49.78
Image height 3.17
Lens total length 16.48
BF 3.81

(Numerical data 3)
Unit mm

Surface data surface number rd nd d d
1 7.295 0.60 1.83481 42.7
2 * 3.377 1.19
3 4.947 0.64 1.95906 17.5
4 4.947 0.45 1.54701 46.2
5 1.941 2.01
6 (F-stop) ∞ 1.03
7 * 8.696 3.74 1.82080 42.7
8 * -3.464 0.12
9 82.587 2.14 1.74100 52.6
10-3.814 0.49 2.10420 17.0
11-15.730 2.93
12 0.20 1.51633 64.1
13 ∞ 1.01
Image plane ∞

Aspheric data second surface
K = 0.00000e + 000 A 4 = -1.88086e-003 A 6 = 1.29962e-004 A 8 = -1.33757e-005

Seventh side
K = 0.00000e + 000 A 4 = -2.70061e-003 A 6 = 3.58514e-004

Eighth side
K = 0.00000e + 000 A 4 = 3.42379e-003 A 6 = 2.16410e-004 A 8 =-1. 74455e-005 A10 = 3.47442e-006

Various data focal length 2.57
F number 2.88
Half angle of view (degree) 50.92
Image height 3.17
Lens total length 16.48
BF 4.07

(Numerical data 4)
Unit mm

Surface data surface number rd nd d d
1 13.480 0.60 1.69680 55.5
2 3.579 1.34
3 * 7.703 0.50 1.69350 53.2
4 * 2.284 1.40
5 12.052 1.72 1.70154 41.2
6-12.052 0.06
7 (F-stop) ∞ 2.31
8 * 9.461 2.27 1.59201 67.0
9 *-3.394 0.10
10 8.922 2.20 1.48749 70.2
11 -6.104 0.45 1.95906 17.5
12 126.862 3.78
Image plane ∞

Aspheric surface data surface 3
K = 0.00000e + 000 A 4 = 2.89811e-003 A 6 =-3.19022e-004

Fourth side
K = 0.00000e + 000 A 4 =-4.69590e-004 A 6 = 9.20615e-004 A 8 =-2.31641e-004 A10 =-6.94765e-005

Eighth side
K = 0.00000e + 000 A 4 = -2.84486e-003 A 6 = 1.65312e-004

9th surface
K = 0.00000e + 000A 4 = 3.59159e-003 A 6 =-9. 10774e-006 A 8 = 3.0 6456e-005

Various data focal length 2.48
F number 2.88
Half angle of view (degree) 51.99
Image height 3.17
Total lens length 16.74
BF 3.78

LA optical system FG front group RG rear group L1 first lens L2 second lens L3 third lens L4 fourth lens L5 fifth lens L6 sixth lens L56 cemented lens SP aperture stop

Claims (10)

Disposed in order from the object side to the image side, a front group having negative refractive power, an aperture stop, consist rear group having positive refractive power, the front group, disposed in order from the object side to the image side, a first It consists of a lens, a second lens, and a third lens,
The rear group comprises, in order from the object side to the image side, a fourth lens of positive refractive power and a cemented lens of negative refractive power ,
The first lens is a negative power lens with a concave surface facing the image side,
The cemented lens is formed by cementing a fifth lens of positive refractive power and a sixth lens of negative refractive power.
When the focal length of the cemented lens is f56 and the focal length of the whole system is f,
-130.0 <f56 / f <-10.0
An optical system characterized by satisfying the following conditional expression. Assuming that the focal length of the fifth lens is f5 and the focal length of the sixth lens is f6,
−1.0 <f6 / f5 <−0.7
An optical system according to claim 1, wherein the following conditional expression is satisfied. When the focal length of the fourth lens is f4
1.2 <f4 / f <2.0
The optical system according to claim 1 or 2, wherein the following conditional expression is satisfied. When the total lens length is D,
4.5 <D / f <8.0
The optical system according to any one of claims 1 to 3, wherein the following conditional expression is satisfied. When the refractive index of the material of the sixth lens is Nd6,
1.85 <Nd6 <2.40
The optical system according to any one of claims 1 to 4, wherein the following conditional expression is satisfied. When the distance in air conversion from the lens surface on the image side of the sixth lens to the image plane is Sk,
Sk / f <2.0
The optical system according to any one of claims 1 to 5, wherein the following conditional expression is satisfied. When one of the second lens and the third lens is a lens Lp, and the lens disposed on the object side of the lens Lp is a lens Ln, the lens Lp has positive refractive power, and the lens Ln is Has negative refractive power,
Assuming that the curvature radius of the lens surface on the image side of the lens Ln is Rn, and the curvature radius of the lens surface on the object side of the lens Lp is Rp,
-10.0 <(Rn + Rp) / (Rn-Rp) <-0.8
The optical system according to any one of claims 1 to 6, wherein the following conditional expression is satisfied.   The second lens is a negative lens whose concave surface faces the image side, the third lens is a positive lens whose convex surface faces the object side, the second lens corresponds to the lens Ln, and the third lens The optical system according to claim 7, wherein the lens Lp corresponds to the lens Lp.   The second lens is a positive lens having a convex surface on the object side, the third lens is a negative lens having a concave surface on the image side, the first lens corresponds to the lens Ln, and the second lens is a second lens. The optical system according to claim 7, wherein the lens Lp corresponds to the lens Lp.   An image pickup apparatus comprising: the optical system according to any one of claims 1 to 9; and a photoelectric conversion element which receives an image formed by the optical system.